Liquid crystal panels have the advantages of being lightweight, thin and low in power consumption and are therefore widely used for liquid TV receivers and also for display devices for personal computers, word processors or the like. On the other hand, liquid crystals per se do not luminesce, so that it is necessary to uniformly illuminate the liquid cyrstal panel from behind and render the liquid crystal screen easily visible, hence a need for a back light. For example, Unexamined Japanese Patent Publication No. SHO 54-90877 and Unexamined Japanese Utility Model Publication No. SHO 54-111985 disclose flat fluorescent lamps for use as back lights.
In recent years, liquid crystals of larger sizes are in use, including, for example, those of A4 size, and there is a need to use flat fluorescent lamps of increased sizes for such large-sized liquid crystal panels. With the flat fluorescent lamps disclosed in the above publications, however, the glass container, when to be made large-sized, must be prepared from a glass plate of increased thickness in order to preclude implosion due to atmospheric pressure, so that the lamp obtained becomes heavier and has an increased thickness.
To overcome this drawback, the present applicant has already proposed a lamp of the construction shown in FIG. 19 (Unexamined Japanese Patent Publication No. SHO 60-188974). The lamp includes reinforcing glass members 10 formed integrally with a lower glass plate 8 by press work for supporting an upper glass plate 6 so as to give the lamp increased resistance to pressure without increasing the thickness thereof.
Nevertheless, the proposed construction requires different molds for liquid crystal panels of different sizes and therefore has the problem of being costly.